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DESCRIPTION
DEMO CIRCUIT 383B
QUICK START GUIDE
LT1930ES5/LT1931ES5
1.2MHz, SOT-23 DC/DC CONVERTER
Demonstration Circuit 383B is multipurpose demonstration board featuring the LT1930 and LT1931. The
demo board offers three separate DC/DC converters.
The Boost circuit is designed to convert 5V input to
12V output at 300mA maximum load. The SEPIC circuit generates constant 12V/300mA output with
10V~16V variable input. The Inverter circuit is designed for applications requiring negative 12V/350mA
from a positive 12V input. All three circuits are designed to demonstrate the advantages of the 1.2MHz
switching frequency, the internal 36V/1A switch, wide
input voltage range and small circuit size. These circuits are intended for space-conscious applications
such as digital cameras, cellular phones, palmtop
computers and LCD displays. The 1.2MHz switching
frequency, 1A integrated switch, small circuit size,
and low component count makes the LT1930 and
LT1931 suitable for use in many other applications,
such as PC cards, miniature disk drives, xDSL power
supplies, flash memory products and local 5V or 12V
supplies.
The LT1930/LT1931 datasheets give complete
descriptions of the parts, their operation and application
information. The datasheets must be read in conjunction
with this quick start guide for working on or modifying
any circuit on the demo circuit 383B.
Design files for this circuit board are available. Call
the LTC factory.
LT is a trademark of Linear Technology Corporation
Table 1. Performance Summary
SYMBOL PARAMETER FOR BOOST CONVERTER CONDITIONS MIN TYP MAX UNITS
V
IN
V
OUT
Ripple V
Fs Switching Frequency 1.2 MHz
SYMBOL PARAMETER FOR SEPIC CONVERTER CONDITIONS MIN TYP MAX UNITS
V
IN
V
OUT
Ripple V
Fs Switching Frequency 1.2 MHz
SYMBOL PARAMETER FOR INVERTING CONVERTER CONDITIONS MIN TYP MAX UNITS
V
IN
V
OUT
Ripple V
Fs Switching Frequency 1.2 MHz
Input Supply Range
Output Voltage Accuracy V
Input Supply Range
Output Voltage Accuracy V
Input Supply Range
Output Voltage Accuracy V
SPECIFICATIONS ARE AT TA = 25°C
IN
IN
IN
IN
IN
IN
= 5V, I
= 5V, I
= 10V, I
=105V, I
= 12V, I
= 12V, I
= 300mA 11.76 12 12.24 V
LOAD
= 300mA 50 mV
LOAD
= 300mA 11.76 12 12.24 V
LOAD
= 300mA 50 mV
LOAD
= 350mA -11.76 -12 -12.24 V
LOAD
= 350mA 40 mV
LOAD
5 V
10 16 V
12 V
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QUICK START PROCEDURES
Refer to Figures 1–4 for proper measurement
equipment setup and follow the procedure outlined
below:
The equipment setup for the three circuits is very
similar. They all have three pins marked “Vin,”
“Gnd” and “Vout,” and a jumper marked “on/off”
for demonstrating the shutdown function.
For the best accuracy it is important to connect true
RMS reading voltmeters directly to the PCB terminals, where the input and output voltage are connected. True RMS reading ammeters should be
used for current measurements.
The SHUTDOWN function is tested by placing the
jumper in the “off” position. This will short the
shutdown pin to ground and turn off the internal
switch of the LT1930/LT1931. Placing the jumper in
the “on” position will return the circuit to normal
operation.
Quick Start for the Boost Circuit:
1. Before turning on the power, connect a 5V, 1A
bench supply to the Vin and Gnd terminals and
connect the output loads (up to 300mA). When an
electronic load is used, decrease load current setting to less than 100mA until the output voltage has
stabilized. Connect an oscilloscope and meters to
the Vout and Gnd terminals, as shown in Figure 1.
2. Turn on the input power supply and observe the
output. The DC383 Boost converter is programmed
to generate 12V from 5V input. The circuit will deliver up to 300mA at 12V.
3. The current limit is tested by increasing the load
past 400mA. The current limit will take effect when
the peak switch current becomes higher than ~1A.
When the current limit is exceeded, the output volt-
age will drop drastically. Return to normal operation
by removing the load.
Quick Start for the SEPIC Circuit:
1. Before turning on the power, connect a 16V, 1A
bench supply to the Vin and Gnd terminals and
connect the output loads (up to 300mA). When an
electronic load is used, decrease load current setting to less than 100mA until the output voltage has
stabilized. Connect oscilloscope and meters to the
Vout and Gnd terminals, as shown in Figure 2.
2. Turn on the input power supply and observe the
output. The DC383 SEPIC Circuit is programmed to
generate 12V from a 10V–16V input. Vary the input
voltage to test the line regulation. The circuit is designed to deliver up to 300mA at a 12V output.
3. The current limit is tested by increasing the load
past 400mA. The current limit will take effect when
the peak switch current becomes higher than ~1A.
When the current limit is exceeded, the output voltage will drop drastically. Return to normal operation
by removing the load.
Quick Start for the Inverter Circuit:
1. Before turning on the power, connect a 12V, 1A
bench supply to the Vin and Gnd terminals and
connect the output loads (up to 300mA). When an
electronic load is used, decrease load current setting to less than 100mA until the output voltage has
stabilized. Connect oscilloscope and meters to the
Vout and Gnd terminals, as shown in Figure 3.
2. Turn on the input power supply and observe the
output. The DC383 Inverter Circuit is programmed
to generate –12V from a +12V input. The circuit will
deliver up to 300mA at –12V.
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3. The current limit is tested by increasing the load
past 500mA. The current limit will take effect when
the peak switch current becomes higher than ~1A.
When the current limit is exceeded, the output voltage will drop drastically. Return to normal operation
by removing the load.
Figure 1. Proper Measurement Equipment Setup for Boost Converter
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Figure 2. Proper Measurement Equipment Setup for Sepic Converter
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Figure 3. Proper Measurement Equipment Setup for Inverting Converter
Figure 4. Proper Input/Output Ripple Measurement Technique
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Authorized Distributor
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DC383B
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